I would have to say I am a beginner with these turbo cars, so I would just like to get more bang for my buck with some easy mods that I can do, I have a $1500 budget on getting the 78 performance better, what should I do then

Have you looked at Rich's site yet? He's got a ton of info as well as a DIY alky injection set up that will help quite a bit. Another simple thing is to add a better flowing exhaust. If you want a better down pipe you'll need to make that yourself, but it's not that hard. Up grading the turbo is some serious $ but you could put a higher stall converter in the car which will help get it out of the hole faster.

First thing first though is if you get the car or not. If you decide to then drive it and see how it behaves. Make sure to put super in it to reduce detonation problems and that it's got clean oil in it. None of the TB cars are cheap or easy but the 78-83 are the hardest for people to understand much less modify. The basic long block will take the exact same mods as the later cars but the rest of the system is where most get screwed up.